To avoid the spinning of driving wheels, it is known in traction control to arrange for an intervention into the wheel brake and, as the case may be, additional intervention into engine management. The wheel brake intervention is executed on wheels subjected to traction slip and permits a differential lock effect. This procedure is based on the consideration of decelerating the wheel subjected to traction slip by way of a defined brake torque to achieve a rotational speed with a favorable predetermined traction slip so that using an open differential gear allows the brake torque generated on one side to be available as an additional drive torque at the other, opposite wheel. Details can be taken from the technical book ‘Fahrsicherheitssysteme’ (Driving Safety Systems), second edition Vieweg 1998, page 75 sqq.
DE 34 21 776 C2 discloses a vehicle with all-wheel drive, wherein the wheels of an axle are connected to the drive shaft and the drive shafts are connected to the driving motor by way of differential gears. An electronic differential lock effect is achieved by introducing a braking pressure on each individual wheel subjected to traction slip. More specifically, braking irrespective of the driver will take place with a corresponding brake torque when traction slip is detected, with a view to reducing the effective drive torque at the spinning wheel. The dosing and modulation of the brake torque is based on slip control on each individual wheel.
A traction control method for use with open differentials is known from the technical journal ATZ 102(2000) No. 9, pages 764–773, wherein, like in anti-lock control, it is detected by evaluation of wheel speed signals whether the wheels are still in a predetermined slip range. During traction control, braking intervention is effected on wheels that exceed the slip threshold. An active braking pressure build-up can prevent a high degree of traction slip on respectively diagonally opposite driving wheels.
A method of detecting so-called axle twist conditions with diagonally opposite slipping driving wheels is disclosed in DE 199 53 773 A1. No hint can be taken from this publication to carry out a detection of driving conditions beyond axle twist conditions.